SINGLE-STEP SUPERFINISHING USING HARD MACHINING RESULTING IN SUPERIOR SURFACE INTEGRITY

Presented are the concept and feasibility of using a single-step hard turning process for superfinishing surfaces that are comparable to bearing races. The following surface integrity requirements of the class of surfaces similar to bearing races are shown to be producible: (1) surface roughness less than 7 mu in., (2) surface waviness less than 60 mu in., (3) cross-sectional crown of 70 mu in., (4) residual stress induced in machining that is favorable for fatigue life, and (5) surface microstructure alteration that is not detrimental to fatigue life. Experimental results of 10 specimens show that the best surface roughness is as good as 1.7 mu in. and can be further improved by optimizing the machining conditions. Residual stress induced by the single-step superfinish hard turning process is more compressive in magnitude and is distributed to a significantly greater depth than that produced by conventional abrasive-based superfinishing.